The goal of this study is to determine the genotypes of the patients with cystic fibrosis followed at the Pittsburgh Center so that this information will be available for translational and clinical studies. Over 500 mutations in the CF gene have been described and there are 4 main types of defects which result from these mutations. Since there are different classes of mutations, it can be expected that some drug therapies will be effective only in treatment of mutations of a specific type. In order to benefit the patients, it is necessary to be aware of their genotypes when specific drug therapies become available for use.